A number of authors provided arguments that a rotating gravastar is a good candidate for a source of the Kerr metric. These arguments were based on the second order perturbation analysis. In the following paper, we construct a perturbative solution of the rotating gravastar up to the third perturbation order and show that once we demand finiteness of the Kretschmann scalar expansion, it cannot be continuously matched with the Kerr spacetime.

We investigate Hawking evaporation of a population of primordial black holes (PBHs) prior to big bang nucleosynthesis as a mechanism to achieve asymmetric reheating of two sectors coupled solely by gravity. While the visible sector is reheated by the inflaton or a modulus, the dark sector is reheated by PBHs. Compared to inflationary or modular reheating of both sectors, there are two advantages: (i) inflaton or moduli mediated operators that can subsequently thermalize the dark sector with the visible sector are not relevant to the asymmetric reheating process and (ii) the mass and abundance of the PBHs provide parametric control of the thermal history of the dark sector, and in particular the ratio of the temperatures of the two sectors. Asymmetric reheating with PBHs turns out to have a particularly rich dark sector phenomenology, which we explore using a single self-interacting real scalar field in the dark sector as a template. Four thermal histories, involving nonrelativistic and relativistic dark matter at chemical equilibrium, followed by the presence or absence of cannibalism, are explored. These histories are then constrained by the observed relic abundance in the current Universe and the Bullet Cluster. The case where PBHs dominate the energy density of the Universe, and reheat both the visible as well as the dark sectors, is also treated in detail.

How rare are extreme-spin primordial black holes? We show how, from an underlying distribution of primordial black hole (PBH) spin, extreme-value statistics can be used to quantify the rarity of spinning PBHs with Kerr parameter close to 1. Using the peaks-over-threshold method, we show how the probability that a PBH forms with spin exceeding a sufficiently high threshold can be calculated using the generalized Pareto distribution. This allows us to estimate the average number of PBHs amongst which we can find a single PBH that formed with spin exceeding a high threshold. We found that the primordial spin distribution gives rise to exceedingly rare near-extremal spin PBHs at formation time: for typical parameter values, roughly up to one in a hundred million PBHs would be formed with spin exceeding the Thorne limit. We discuss conditions under which even more extreme-spin PBHs may be produced, including modifying the skewness and kurtosis of the spin distribution via a smooth transformation. We deduce from our calculations that, if indeed asteroid-mass PBHs above the current observational limit on evaporating PBHs of mass $\sim {10}^{17}\mathrm{g}$ contribute significantly to the dark matter, it is very likely that some of them at somewhat lower masses could be long-lived near-extremal PBHs.

We investigate the structure and the tidal deformability of strange stars with a mirror-dark-matter core for the standard MIT bag model. We find that to explain the observations of GW170817, PSR $\mathrm{J}0740+6620$ and PSR $\mathrm{J}0030+0451$ simultaneously, strange stars in GW170817 should have a mirror-dark-matter core although it is unnecessary for PSR $\mathrm{J}0740+6620$ and PSR $\mathrm{J}0030+0451$ to contain one. More generally, our study leads to the result that for the standard MIT bag model, the observations of compact stars mentioned above could serve as evidence for the existence of a dark-matter core inside strange stars.

We propose a gauged two-Higgs-doublet model featuring an anomalous Peccei-Quinn symmetry, $U(1{)}_{PQ}$. Dangerous tree-level flavor-changing neutral currents, common in two-Higgs-doublet models, are forbidden by the extra gauge symmetry, $U(1{)}_X$. In our construction, the solutions to the important issues of neutrino masses, dark matter, and the strong $CP$ problems are interrelated. Neutrino masses are generated via a Dirac seesaw mechanism and are suppressed by the ratio of the $U(1{)}_X$ and the $U(1{)}_{PQ}$ breaking scales. Naturally small neutrino masses suggest that the breaking of $U(1{)}_X$ occurs at a relatively low scale, which may lead to observable signals in near-future experiments. Interestingly, spontaneous symmetry breaking does not lead to mixing between the $U(1{)}_X$ gauge boson, $Z^{\prime }$, and the standard $Z$. For the expected large values of the $U(1{)}_{PQ}$ scale, the associated axion becomes “invisible,” with Dine-Fischler-Srednicki-Zhitnitsky-like couplings, and may account for the observed abundance of cold dark matter. Moreover, a viable parameter space region, which falls within the expected sensitivities of forthcoming axion searches, is identified. We also observe that the flavor-violating process of kaon decaying into pion plus axion, $K^{+}\to {\pi }^{+}a$, is further suppressed by the $U(1{)}_X$ scale, providing a rather weak lower bound for the axion decay constant $f_a$.

This work presents a first full one-loop computation of vector boson scattering (VBS) within the non-linear effective field theory given by the bosonic sector of the usually called electroweak chiral Lagrangian (EChL). The computation is performed in the most general case of covariant $R_{\xi }$ gauges and is compared through all this work with the Standard Model case, whose computation in these covariant gauges is also novel and is presented also here. The calculation of the one-loop VBS amplitude is performed using the diagrammatic method by means of the one-particle-irreducible (1PI) Green functions that are involved in these scattering processes. The central part of this work is then devoted to the renormalization of all the $n$-legs one-loop 1PI Green functions involved. This renormalization is performed in the most general off-shell case with arbitrary external legs momenta. We then describe in full detail the renormalization program, which within this context of the EChL, implies to derive all the counterterms for both the electroweak parameters, like boson masses and gauge couplings, and those for the EChL coefficients. These later are crucial for the renormalization of the new divergences typically appearing when computing loops with the lowest chiral dimension Lagrangian. We present here the full list of involved divergences and counterterms in the $R_{\xi }$ gauges and derive the complete set of renormalization group equations for the EChL coefficients. In the last part of this work, we present the EChL numerical results for the one-loop cross section in the $WZ$ channel and compare them with the SM results.

We discuss photon-photon fusion mechanisms of dilepton production in proton-proton collisions with rapidity gap in the main detector and one forward proton in the forward proton detectors. This is relevant for the LHC measurements by $\mathrm{ATLAS}+\mathrm{AFP}$ and $\mathrm{CMS}+\mathrm{PPS}$. Transverse momenta of the intermediate photons are taken into account and photon fluxes are expressed in terms of proton electromagnetic form factors and structure functions. Differential distributions in ${\xi }_{1/2}$, $M_{ll}$, $Y_{ll}$, $p_{t,ll}$, $M_R$ are shown, and the competition of different mechanisms is discussed. Both double-elastic and single-dissociative processes are included in the analysis. Different parametrizations of the structure functions are used. We discuss also mechanism with one forward ${\mathrm{\Delta }}^{+}$ isobar or other proton resonances in the final state. The role of several cuts is studied. We also use the superchic generator and compare corresponding results to the results of our codes. The soft rapidity gap survival factor is calculated for each contribution separately. The gap survival factor for the single-dissociative mechanism due to minijet emission into the main detector is calculated in addition. It depends on the type of contribution (fully elastic, single dissociation, double dissociation). The soft rapidity gap survival factor for the case of single proton measurement is significantly smaller than that for the inclusive case (no proton measurement). We find only weak dependence on the invariant mass of the dilepton system as well as the lepton pair transverse momentum and sizeable dependence on the pair rapidity. The latter effect is rather difficult to identify experimentally.

We employ the analytic QCD (anQCD) approach to analyze the unpolarized nucleon structure function in deep inelastic scattering processes at next-to-leading-order accuracy. Considering the unreliable results of the underlying perturbative QCD (pQCD) at energy scales near to QCD cut off parameter $Q^2\sim {\mathrm{\Lambda }}^2$ and below, we modify the calculations at these scales using the anQCD approach and compare them with results from underlying pQCD and the available experimental data. The massive perturbation theory model is also used where an effective mass is attributed to gluons. Finally, we use the Jacobi polynomials formalism to transfer the calculations from Mellin moment space to Bjorken-$x$ space. To confirm the validity of the anQCD approach the Gottfried sum rule is also investigated. The achieved numerical results at low energy scales are compatible with what is expected and correspond to an admissible behavior of parton densities.

We propose a new semileptonic tag method to study the doubly Cabibbo-suppressed $D$ decay in $\psi (3770)\to D\overline{D}$ reaction. Utilizing the dataset corresponding to an integrated luminosity of $2.93{\mathrm{fb}}^{-1}$ at a center-of-mass energy of 3.773 GeV collected by the BESIII detector, we determine the branching fraction for $D^{+}\to K^{+}{\pi }^{+}{\pi }^{-}{\pi }^0$ to be $(1.03\pm 0.12_{\mathrm{stat}}\pm 0.06_{\mathrm{syst}})\times {10}^{-3}$, in which the contributions from narrow intermediate resonances, $D^{+}\to K^{+}\eta$, $D^{+}\to K^{+}\omega$, and $D^{+}\to K^{+}\varphi$ have been excluded. Combining the world average of the branching fraction of $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^0$, we determine $\mathcal{B}(D^{+}\to K^{+}{\pi }^{+}{\pi }^{-}{\pi }^0)/\mathcal{B}(D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^0)=(1.65\pm 0.21)\%$, corresponding to $(5.73\pm 0.73){\tan }^4{\theta }_c$, where ${\theta }_c$ is the Cabibbo mixing angle. These results are consistent with our previous measurement with hadronic tags but are significantly larger than other doubly Cabibbo-suppressed decays in the charm sector.

We construct a semiholographic effective theory in which the electron of a two-dimensional band hybridizes with a fermionic operator of a critical holographic sector, while also interacting with other bands that preserve quasiparticle characteristics. Besides the scaling dimension $\nu$ of the fermionic operator in the holographic sector, the effective theory has two dimensionless couplings $\alpha$ and $\gamma$ determining the holographic and Fermi-liquid-type contributions to the self-energy respectively. We find that irrespective of the choice of the holographic critical sector, there exists a ratio of the effective couplings for which we obtain linear-in-$T$ resistivity for a wide range of temperatures. This scaling persists to arbitrarily low temperatures when $\nu$ approaches unity in which limit we obtain a marginal Fermi liquid with a specific temperature dependence of the self-energy.

We investigate the interplay between gravity and the quantum coherence present in the state of a pulse of light propagating in curved spacetime. We first introduce an operational way to distinguish between the overall shift in the pulse wave packet and its genuine deformation after propagation. We then apply our technique to quantum states of photons that are coherent in the frequency degree of freedom, as well as to states of completely incoherent light. We focus on Gaussian profiles and frequency combs and find that the quantum coherence initially present can enhance the deformation induced by propagation in a curved background. These results further support the claim that genuine quantum features, such as quantum coherence, can be used to probe the gravitational properties of physical systems. We specialize our techniques to Earth-to-satellite communication setups, where the effects of gravity are weak but can be tested with current satellite technologies.

We present a comparison of the AQFT-based Fewster-Verch framework with the Unruh-DeWitt particle detector models commonly employed in relativistic quantum information and QFT in curved space. We use this comparison to respond to a recent paper [M. H. Ruep, Weakly coupled local particle detectors cannot harvest entanglement, arXiv:2103.13400.] in which it was argued that the Reeh-Schlieder theorem prevents weakly coupled local particle detectors from harvesting vacuum entanglement from a quantum field. Their claim can be traced back to the mixedness that a local particle detector cannot escape from because of the entanglement that it must have with the quantum fields outside of the localization area. We argue that for any realistic scale of localization for physical particle detectors, the effect of that mixedness is negligible, and that weakly coupled, localized particle detectors are not impeded from harvesting vacuum entanglement.

The definition of well-behaved coordinate charts for black hole spacetimes can be tricky, as they can lead for example to either unphysical coordinate singularities in the metric (e.g., $r=2M$ in the Schwarzschild black hole) or to an implicit dependence of the chosen coordinates to physical relevant coordinates (e.g., the dependence of the null coordinates in the Kruskal metric). Here we discuss two approaches for coordinate choices in spherically symmetric spacetimes allowing us to explicitly discuss “solitary” and spherically symmetric black holes from a regular horizon to null infinity. The first approach relies on a construction of a regular null coordinate system (where regular is meant as being defined from the horizon to null infinity) given an explicit solution of the Einstein-matter equations. The second approach is based on an affine-null formulation of the Einstein equations and the respective characteristic initial value problem. In particular, we present a derivation of the Reissner-Nordström black holes expressed in terms of these regular coordinates.

In this paper we study the accretion of matter onto the black holes and the shadow images obtained by an infalling accretion flow of gas in a theory of massive gravity with a spontaneously breaking Lorentz symmetry. This black hole solution is characterized by mass $M$, scalar charge $S$, and the parameter $\lambda$. In order to extract the astrophysical results of our analyses, first, we have assumed a specific range for the parameter $\lambda$ to constrain the scalar charge $S$ using the Event Horizon Telescope (EHT) result. To this end, we have studied the effect of the scalar charge on the intensity of the electromagnetic radiation from the black hole. Moreover, we investigate the behavior of polytropic as well as the isothermal fluid flow onto massive gravity black hole and notice that accretion starts from supersonic/subsonic flow, passes through the critical point using particular model parameter and ends near the horizon. We also analyzed the mass accretion rate in the presence of various fluids which indicates important signatures. We also elaborate on the possibility to analyze the phase transition and the stability of the black hole using the shadow formalism.

In this work, we study the relation of the eikonal quasinormal modes (EQNMs) and the unstable fundamental photon orbits (UFPOs) in the Kerr-Newman spacetime. We find that in the eikonal limit the gravitational and electromagnetic perturbations of the Kerr-Newman black hole are naturally decoupled, and a single one-dimensional Schrödinger-like equation encoding the QNM spectrum can be derived. We then show that the decoupled Teukolsky master equation and the Klein-Gordon equation for the massless scalar field in the Kerr-Newman spacetime are of the same form in the eikonal limit. As a direct consequence, taking into account of the boundary conditions for EQNMs we show an exact correspondence between EQNMs and UFPOs, that is, EQNM/UFPO correspondence. More precisely, similar to the Kerr case, the real part of EQNM’s frequency is a linear combination of the precessional and (polar) orbital frequencies, while the imaginary part of the frequency is proportional to the Lyapunov exponent of the UFPO.

Motivated by exploring the interface between thermodynamics of spacetime and quantum gravity effects, we develop a heuristic derivation of Hawking temperature and Bekenstein entropy from the existence of a minimal resolvable area. Moreover, we find leading order quantum gravity corrections to them that are in qualitative agreement with results obtained by other methods, both heuristic and rigorous. In this way, we recover, as a particular case, the corrections heuristically obtained from the existence of minimal length. We also show that the size of minimal area is constrained from above by well-understood results of semiclassical black hole physics, specifically by the entropy content of Hawking radiation. The minimal area derivation we introduce is also applied to finding the Unruh temperature associated with causal diamonds and to establish a new relation between this temperature and the entropy of the causal diamond’s horizon.

We present covariant symmetry operators for the conformal wave equation in the (off-shell) Kerr–NUT–AdS spacetimes. These operators, that are constructed from the principal Killing–Yano tensor, its ‘symmetry descendants’, and the curvature tensor, guarantee separability of the conformal wave equation in these spacetimes. We next discuss how these operators give rise to a full set of conformally invariant mutually commuting operators for the conformally rescaled spacetimes and underlie the $R$-separability of the conformal wave equation therein. Finally, by employing the WKB approximation we derive the associated Hamilton–Jacobi equation with a scalar curvature potential term and show its separability in the Kerr–NUT–AdS spacetimes.

The origin and composition of ultrahigh energy cosmic rays (UHECRs) remains a mystery. The common lore is that UHECRs are deflected from their primary directions by the Galactic and extragalactic magnetic fields. Here we describe an extragalactic contribution to the deflection of UHECRs that does not depend on the strength and orientation of the initial seed field. Using the IllustrisTNG simulations, we show that outflow-driven magnetic bubbles created by feedback processes during galaxy formation deflect approximately half of all ${10}^{20}\mathrm{eV}$ protons by 1° or more, and up to 20°–30°. This implies that the deflection in the intergalactic medium must be taken into account in order to identify the sources of UHECRs.

The simplest $\alpha$-attractor $T$ model is given by the potential $V=V_0{\tanh }^2(\lambda \varphi /M_{\mathrm{pl}})$. However its generalization to the class of models of the type $V=V_0{\tanh }^p(\lambda \varphi /M_{\mathrm{pl}})$ is difficult to interpret as a model of inflation for most values of $p$. Keeping the basic model, we propose a new generalization, where the final potential is of the form $V=V_0(1-{\mathrm{sech}}^p(\lambda \varphi /M_{\mathrm{pl}}))$, which does not present any of the problems that plague the original generalization, allowing a successful interpretation as a model of inflation for any value of $p$ and, at the same time, providing the potential with a region where reheating can occur for any $p$ (including odd and fractional values) without difficulty. In the cases $p=1$, 2, 4 we obtain the solutions $r(n_s,N_{ke})$ where $r$ is the tensor-to-scalar ratio, $n_s$ the spectral index and $N_{ke}$ the number of $e$-folds during inflation. We also show how these solutions connect to the ${\varphi }^2$ monomial.

Lattice results on sigma terms and global analysis of parton momentum fractions are used to give the quark and glue fractions of the proton mass and rest energy. The mass decomposition in terms of the trace of the energy-momentum tensor is renormalization group invariant. The decomposition of the rest energy from the Hamiltonian and the gravitational form factors are scheme and scale dependent. The separation of the energy-momentum tensor into the traceless part, which is composed of the quark and glue parton momentum fractions, and the trace part has the minimum scheme dependence. We identify the glue part of the trace anomaly $⟨H_{\beta }⟩$ as the vacuum energy from the glue condensate in the vacuum. From the metric term of the gravitational form factors, which is the stress part of the stress-energy-momentum tensor, we find that the trace part of the rest energy, dominated by $⟨H_{\beta }⟩$, gives a constant restoring pressure that balances that from the traceless part of the Hamiltonian to confine the hadron, much like the cosmological constant Einstein introduced for a static universe. From a lattice calculation of $⟨H_{\beta }⟩$ in the charmonium, we deduce the associated string tension, which turns out to be in good agreement with that from a Cornell potential, which fits the charmonium spectrum.